Title: humic substances
Long Title: IUPAC Gold Book - humic substances
DOI: 10.1351/goldbook.14746
Status: current

Definition
Nonvolatile organic anionic polyelectrolytes, of biological origin, in the molecular mass range \(\pu{500\!{-}\! 5000}\), which have complex structures and are variable in composition.

Note
Humic substances occur naturally as deposits on sediment and soil particles and constitute \(\pu{30\!{-}\! 50 \%}\) of the dissolved organic carbon (DOC) in natural waters. Humic substances are classified according to solubility and may contain humic acid, fulvic acid, and humin.

Related Terms
- dissolved organic carbon: https://goldbook.iupac.org//terms/view/14595
- fulvic acid: https://goldbook.iupac.org//terms/view/14703
- soil: https://goldbook.iupac.org//terms/view/15036

Source
- PAC, 2009, 81, 829. 'Glossary of terms used in ecotoxicology (IUPAC Recommendations 2009)' on page 897 (https://doi.org/10.1351/PAC-REC-08-07-09)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/14746/html
- json: https://goldbook.iupac.org/terms/view/14746/json
- xml: https://goldbook.iupac.org/terms/view/14746/xml

Citation: Citation: 'humic substances' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.14746
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Accessed: 2026-04-18T01:58:25+00:00